DEV: Improve Guardian devex (#24706)

It's quite confusing for blank? to be overridden
on AnonymousUser and BasicUser to represent
whether the fake user is authenticated or not;
we can achieve the same thing more clearly with
a wrapper GuardianUser class around these
user classes. Also fixes an issue where
`def user` would be returning nil.

lib/guardian.rb

@@ -11,6 +11,36 @@ require "guardian/tag_guardian"
 require "guardian/topic_guardian"
 require "guardian/user_guardian"
 
+class GuardianUser
+  def initialize(user_alike)
+    @user_alike = user_alike
+  end
+
+  def actual
+    @user_alike
+  end
+
+  def fake?
+    if @user_alike.respond_to?(:fake?)
+      @user_alike.fake?
+    else
+      false
+    end
+  end
+
+  def authenticated?
+    if @user_alike.respond_to?(:authenticated?)
+      @user_alike.authenticated?
+    else
+      true
+    end
+  end
+
+  def method_missing(method, *args, &block)
+    @user_alike.public_send(method, *args, &block)
+  end
+end
+
 # The guardian is responsible for confirming access to various site resources and operations
 class Guardian
   include BookmarkGuardian
@@ -28,6 +58,12 @@ class Guardian
     def blank?
       true
     end
+    def fake?
+      true
+    end
+    def authenticated?
+      false
+    end
     def admin?
       false
     end
@@ -84,7 +120,13 @@ class Guardian
   # categories or PMs but can read public topics.
   class BasicUser
     def blank?
-      false
+      true
+    end
+    def fake?
+      true
+    end
+    def authenticated?
+      true
     end
     def admin?
       false
@@ -139,7 +181,8 @@ class Guardian
   attr_reader :request
 
   def initialize(user = nil, request = nil)
-    @user = user.presence || AnonymousUser.new
+    @guardian_user = GuardianUser.new(user.presence || AnonymousUser.new)
+    @user = @guardian_user.actual
     @request = request
   end
 
@@ -152,7 +195,7 @@ class Guardian
   end
 
   def user
-    @user.presence
+    @guardian_user.fake? ? nil : @user
   end
   alias current_user user
 
@@ -161,7 +204,7 @@ class Guardian
   end
 
   def authenticated?
-    @user.present?
+    @guardian_user.authenticated?
   end
 
   def is_admin?